The present invention relates to a method for maintaining the reliability of a storage device and, more particularly, to a storage device capable of holding high-density recorded information in a semi-permanently reproducible state.
An example of a disk drive control system known in the art is illustrated in FIG. 5 along with a portion of the control system of a host computer. In FIG. 5, reference numeral 25 denotes a control circuit system of the disk drive, and reference numeral 21 denotes part of the control system of the host computer. This disk drive control system 25 includes an interface section 4, a read/write control section 5, a head position control section 6, and a spindle motor control section 7. The interface section 4 is connected to the read/write control section 5, the head position control section 6, the spindle motor control section 7, and a disk drive interface section 11 in the host computer 21. In addition, the read/write control section 5, the head position control section 6 and the spindle motor control section 7 are respectively connected to a read/write head 8, a head carriage 9 and a spindle motor 10. An instruction from the host computer 21 is sent to the interface section 4 of the disk drive control system 25 through the disk drive interface section 11 in the host computer 21, so that reading/writing of information is performed. When reading/writing is performed, a disk is rotated by the spindle motor 10. Then, the read/write head 8 is moved to a desired track by head carriage 9 so that the formation and detection of recorded magnetization can be performed by the read/write head 8. These operations are respectively controlled by the spindle motor control section 7, the head position control section 6 and the read/write control section 5. A disk drive having the above-described type of arrangement is disclosed in, for example, xe2x80x9cTransistor Technology Special, The whole Technique for Utilizing Hard Disks and SCSI, p. 8 (CQ Publishing Company).
Once information is recorded in a conventional disk drive, the information is not copied as long as a person does not give the disk drive a specific instruction to copy. This is because magnetic recording has been considered to be a recording method that is capable of semi-permanently holding information recorded once, in the form of recorded magnetization.
However, if magnetic particles are reduced in size or a medium is made from a thin film in order to increase the recording density of magnetic recording, the recorded magnetization of each bit will weaken with time, due to influences such as from thermal fluctuation. It has been discovered that this phenomenon is particularly serious at high temperatures. This is disclosed in the Journal of Applied Physics 75 (10) (May 1994), IEEE Transactions on Magnetics, Vol. 30, No. 6, (1994), and the Technical Report of the Institute of Electronics, Information and Communication Engineers of Japan, MR94-105, pp. 25-30 (March, 1995)xe2x80x9d and so on.
In IEEE Transactions on Magnetics, Vol. 32, No. 1, (Jan. 1996), it is reported that in the case of a medium using a soft magnetic under layer, the reproduced output may decrease with time. A decrease in recorded magnetization leads to the problem that the reliability of the storage device is impaired because information cannot be correctly reproduced.
The process of conducting a self-diagnosis and predicting trouble (SMART) has been proposed as a means for maintaining or improving the reliability of a disk drive. According to this process, a warning is issued to a host if the number of seek errors or retries during normal use exceeds a reference value. This process is disclosed in DATAQUEST ALERT (Apr. 17, 1995). However, in this method, since no warning is issued until an abnormality occurs during normal use, there is a risk that it will be too late to securely restore data when recorded magnetization of the medium has become small.
It is an object of the present invention is to solve the above-described problems of the prior art and hold high-density recorded information in a semi-permanently reproducible state, thereby maintaining the reliability of storage devices.
To achieve this object, a storage device according to the present invention has at least one recording medium, a medium driving section for driving the recording medium, a read/write head for reading/writing information from/to the recording medium, a head positioning section for driving the read/write head, and a control system for processing a recording signal to be sent to a write head and a reproduced signal sent from a read head, and for processing a control signal for the medium driving section and the head positioning section. The storage device additionally includes a time counting device, a cache memory and a copy control circuit, and periodically and automatically copies information recorded in the storage device.
More specifically, in the embodiment shown in FIG. 1, a disk drive includes at least an interface section 4, a read/write control section 5, a head position control section 6 and a spindle motor control section 7, each of which is connected to the interface section 4, a read/write head 8 connected to the read/write control section 5, a head carriage 9 connected to the head position control section 6, and a spindle motor 10 connected to the spindle motor control section 7. The storage device additionally includes a first timing counting device 1, a cache memory 2 and a copy control circuit 3, the copy control circuit 3 is connected to each of the timing counting device 1, the cache memory 2, the interface section 4, the read/write control section 5, the head position control section 6 and the spindle motor control section 7, and the disk drive periodically transmits from the timing counting device 1 a signal for actuating the copy control circuit 3, sequentially reproducing information previously recorded in the disk drive, temporarily storing the information in the cache memory 2, and again automatically recording the information into the disk, i.e. performing copying.
A storage device according to the present invention includes at least one recording medium, a medium driving section for driving the recording medium, a read/write head for reading/writing information from/to the recording medium, a head positioning section for driving the read/write head, and a control system for processing a recording signal to be sent to a write head and a reproduced signal sent from a read head, and for processing a control signal for the medium driving section and the head positioning section. The storage device additionally includes a time counting device, a cache memory, a copy control circuit and a reference control circuit, and has a function to automatically copy information which remains recorded for a predetermined time after the last recording date on which arbitrary information has been recorded, from the information previously recorded in the storage device.
Specifically, in the embodiment shown in FIG. 2, a disk drive at least comprises an interface section 4, a read/write control section 5, a head position control section 6, a spindle motor control section 7, each of the three sections 5, 6 and 7 being connected to the interface section 4, a read/write head 8 connected to the read/write control section 5, a head carriage 9 connected to the head position control section 6, and a spindle motor 10 connected to the spindle motor control section 7. The storage device additionally includes a cache memory 2, a copy control circuit 3, a reference control circuit 12, a first time counting device 13 and a second time counting device 14, the copy control circuit 3 is connected to each of the cache memory 2, the interface section 4, the read/write control section 5, the head position control section 6, the spindle motor control section 7 and the reference control circuit 12, the reference control circuit 12 is connected to each of the interface section 4, the read/write control section 5, the head position control section 6, the spindle motor control section 7, the first time counting device 13 and the second time counting device 14, the storage device has a function to periodically transmit a signal for actuating the reference control circuit 12 from the first time counting device 13, search for information which remains recorded for a predetermined time or more after the last recording date, in the information previously recorded in the disk drive, while making reference to the present year, month and day outputted from the second time counting device 14, transfer the name of the information to the copy control circuit 3, sequentially reproduce the corresponding information, temporarily store the information in the cache memory 2 and thereafter again automatically record the stored information in the disk drive, i.e. performing copying.
A storage device according to the present invention includes at least one recording medium, a medium driving section for driving the recording medium, a read/write head for reading/writing information from/to the recording medium, a head positioning section for driving the read/write head, and a control system for processing a recording signal to be sent to a write head and a reproduced signal sent from a read head, and for processing a control signal for the medium driving section and the head positioning section. The storage device additionally includes a time counting device, a cache memory, a copy control circuit and a reproduced output detect circuit, and records a predetermined signal in part of the storage device in advance, periodically measures the reproduced output of the signal and, if the reproduced output is smaller than a predetermined reference value, again record the signal, and automatically copying information recorded in the storage device. Specifically, in the embodiment shown in FIG. 3, a disk drive at least comprises an interface section 4, a read/write control section 5, a head position control section 6, a spindle motor control section 7, each of the three sections 5, 6 and 7 being connected to the interface section 4, a read/write head 8 connected to the read/write control section 5, a head carriage 9 connected to the head position control section 6, and a spindle motor 10 connected to the spindle motor control section 7. The storage device additionally includes a cache memory 2, a copy control circuit 3, a time counting device 13 and a reproduced output detect circuit 17, the copy control circuit 3 is connected to each of the cache memory 2, the interface section 4, the read/write control section 5, the head position control section 6, the spindle motor control section 7 and the reproduced output detect circuit 17, the reproduced output detect circuit 17 is connected to each of the read/write control section 5, the head position control section 6, the spindle motor control section 7 and the time counting device 13, and has a function to record a predetermined reference signal in part of the disk drive in advance, periodically transmit from the first time counting device 13 a signal for actuating the reproduced output detect circuit 17, measure the reproduced output of the reference signal, and, if the reproduced output is smaller than a predetermined reference value, transmit from the reproduced output detect circuit 17 a signal for actuating the copy control circuit 3, again record the reference signal, and automatically copying information recorded in the disk device 23.
Any of the above storage devices according to the present invention also have a function to automatically copy information recorded in the storage device to the storage device or to another storage device if the temperature in the storage device is higher than a predetermined reference value. These storage devices further include a thermometer and a time counting device, and has a function to automatically copy the information recorded in the storage device to the storage device or to another storage device at intervals of period shorter than that during normal temperature if the temperature in the storage device is higher than the predetermined reference value.
For example, in the embodiment shown in FIG. 4 in which this method is added to the embodiment shown in FIG. 1, a disk drive at least comprises an interface section 4, a read/write control section 5, a head position control section 6, a spindle motor control section 7, each of the three sections 5, 6 and 7 being connected to the interface section 4, a read/write head 8 connected to the read/write control section 5, a head carriage 9 connected to the head position control section 6, and a spindle motor 10 connected to the spindle motor control section 7, and is characterized in that the storage device additionally comprises a first timing counting device 1, a cache memory 2, a copy control circuit 3, a thermometer 18 and a second time counting device 19, the copy control circuit 3 is connected to each of the first timing counting device 1, the cache memory 2, the interface section 4, the read/write control section 5, the head position control section 6, the spindle motor control section 7, the thermometer 18 and the second time counting device 19, the disk drive has, in addition to the function to periodically and automatically copy information, a function to measure the temperature in the disk drive with the thermometer 18 at all times during the operation of the disk drive and, if the temperature is higher than a predetermined reference value, transmit from the thermometer 18 a signal for actuating the second time counting device 19, transmit from the second time counting device 19 a signal for actuating the copy control circuit 3 at intervals of period shorter than that during normal temperature, and automatically copy information recorded in the disk device to the disk drive or another disk drive.
These and other objects, features and advantages of the present invention will become more apparent in view of the following detailed description of the preferred embodiments in conjunction with the drawings.